This invention relates to electrostatographic imaging systems and more particularly to an improved blade cleaning apparatus for cleaning electrostatographic image developer material from an imaging surface.
One method for cleaning of electrostatographic plates is disclosed in U.S. Pat. No. 3,552,850, to Royka et al. A flexible cleaning blade is used in pressure contact at the photoconductive surface to remove residual toner particles. Royka et al. also disclose that a dry solid lubricant may be supplied to the electrostatographic plate.
It is also known to supply slow translation to the cleaning blade in an electrostatographic plate cleaning apparatus. Such translation systems are described in detail in U.S. Pat. Nos. 3,724,019 to Shanley; 3,724,020 to Till; 3,740,789 to Ticknor; 3,847,480 to Fisher; and 3,854,814 to Jones. The systems described in the Shanley, Till, and Ticknor patents are similar in many respects to those employed commercially in the Xerox 3100 and 4000 copiers. In those systems the blade is slowly moved parallel to the drum axis in a reciprocal fashion. One of the features of those systems is that the slow sideways translation of the blade distributes the wear caused by an individual drum asperity over a relative large portion of the blade edge. This consequently extends blade life and reduces the occurrence of cleaning failures. It has also been found that slow translation of the blade for a few seconds after the drum had stopped is beneficial in breaking up particle accumulation developed between the blade and the photoconductive surface, thereby providing improved cleaning.
Copiers employing blade cleaning systems can be subject to random cleaning failures which can result in undesirable print-out on the copy sheet. For example, "toner streaking" which can print-out can be caused by a local "tuck under" or folding under of the blade edge which allows the toner to pass under the blade. Lubricants are employed in the commercial copiers to reduce the occurrence of such tuck-unders. In one system a particulate lubricant is employed which forms a seal between the blade and the photoconductive surface to provide effective blade cleaning. It has been observed, however, that the toner build-up in front of the cleaning blade is not always a loose fluffy powder as might be expected. In fact, it frequently is a relatively solid closely packed mass. The solidity of the clean toner is especially evident when there has been a cleaning failure. It is possible that hard packed toner inhibits reliable lubrication and sealing of the blade, thereby increasing the liklihood of a cleaning failure.
Yet another type of cleaning failure which can occur in electrostatographic systems comprises a "developer side seal failure". In this instance toner is impacted on the drum surface ends through the action of the developer housing end seals against the drum surface. The impacted toner which build-up on the ends of the drum surface lies generally outside the imaging area. Normally the cleaning blade extends across the entire drum surface including the area of the side seal failure. However, if the side seal failure is not effectively cleaned by the cleaning system then the impacted toner can build-up and spread into the imaging area, and print-out on the resulting copy sheets.
It has been found that improved cleaning with a blade cleaning system can be obtained by rapidly vibrating the blade. This approach has been found to provide an improvement over the systems of Shanley and Till, particularly with respect to the elimination of side seal failures.
In U.S. Pat. No. 3,617,123 to Emerson, a method and apparatus for cleaning residual toner material is provided wherein a brush mounted at the entrance to a development-cleaning station is vibrated to uniformly distribute residual toner over the entire area of the photoconductive surface to improve cleaning. The brush itself does not remove the toner.
In addition to the foregoing patents, numerous patents exist in fields outside electrostatography, which deal with the use of reciprocating, oscillatory, or vibrating doctor blades. Exemplary of oscillatory systems are U.S. Pat. Nos. 2,300,908; 2,544,557; 2,857,612; 2,972,767; and 3,130,439. Exemplary of vibrating systems are U.S. Pat. Nos. 2,885,069; 3,087,184; 3,389,655; and 3,617,123. U.S. Pat. No. 3,087,184 in particular shows the use of a vibrating doctor blade mechanism to provide a self-cleaning action for the blade.
In blade cleaning of toner, the toner is not being doctored, rather the toner is preferably totally stopped by the cleaning blade or blades in a single rotation of the photoreceptor drum or surface, and simultaneously or subsequently removed from the surface. The entire surface must be cleaned thousands of times without damage. The cleaning loads on the blade are very uneven, both short term and long term, because the location, density and tenacity of the residual toner varies widely over the surface, depending on the images, the exposures, the surface charges, the toner development, the image border areas, etc. Furthermore, the frictional forces of the cleaning operation, unless carefully controlled, can easily result in the generation of excessive pressure or heat, resulting in physical and chemical changes in the toner, smearing of toner materials onto the photoreceptor, or blade, excessive photoreceptor wear, or other problems, especially in higher speed machines. Thus, cleaning dry toner from a photoreceptor presents extremely critical requirements not normally found in other cleaning fields, and blade cleaning systems suitable for other fields and applications, e.g., cleaning or doctoring systems for metal gravure rollers or inking rollers or paper mill rollers or adhesive applicators, are not normally appropriate.